/***************************************************************************/
/*                                                                         */
/*  afwarp.c                                                               */
/*                                                                         */
/*    Auto-fitter warping algorithm (body).                                */
/*                                                                         */
/*  Copyright 2006, 2007, 2011 by                                          */
/*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
/*                                                                         */
/*  This file is part of the FreeType project, and may only be used,       */
/*  modified, and distributed under the terms of the FreeType project      */
/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/***************************************************************************/


/*
 *  The idea of the warping code is to slightly scale and shift a glyph
 *  within a single dimension so that as much of its segments are aligned
 *  (more or less) on the grid.  To find out the optimal scaling and
 *  shifting value, various parameter combinations are tried and scored.
 */

#include "afwarp.h"

#ifdef AF_CONFIG_OPTION_USE_WARPER

/*************************************************************************/
/*                                                                       */
/* The macro FT_COMPONENT is used in trace mode.  It is an implicit      */
/* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log  */
/* messages during execution.                                            */
/*                                                                       */
#undef  FT_COMPONENT
#define FT_COMPONENT  trace_afwarp


/* The weights cover the range 0/64 - 63/64 of a pixel.  Obviously, */
/* values around a half pixel (which means exactly between two grid */
/* lines) gets the worst weight.                                    */
#if 1
static const AF_WarpScore
af_warper_weights[64] =
{
  35, 32, 30, 25, 20, 15, 12, 10,  5,  1,  0,  0,  0,  0,  0,  0,
   0,  0,  0,  0,  0,  0, -1, -2, -5, -8,-10,-10,-20,-20,-30,-30,

 -30,-30,-20,-20,-10,-10, -8, -5, -2, -1,  0,  0,  0,  0,  0,  0,
   0,  0,  0,  0,  0,  0,  0,  1,  5, 10, 12, 15, 20, 25, 30, 32,
};
#else
static const AF_WarpScore
af_warper_weights[64] =
{
  30, 20, 10,  5,  4,  4,  3,  2,  1,  0,  0,  0,  0,  0,  0,  0,
   0,  0,  0,  0,  0,  0,  0, -1, -2, -2, -5, -5,-10,-10,-15,-20,

 -20,-15,-15,-10,-10, -5, -5, -2, -2, -1,  0,  0,  0,  0,  0,  0,
   0,  0,  0,  0,  0,  0,  0,  0,  1,  2,  3,  4,  4,  5, 10, 20,
};
#endif


/* Score segments for a given `scale' and `delta' in the range */
/* `xx1' to `xx2', and store the best result in `warper'.  If  */
/* the new best score is equal to the old one, prefer the      */
/* value with a smaller distortion (around `base_distort').    */

static void
af_warper_compute_line_best( AF_Warper     warper,
                             FT_Fixed      scale,
                             FT_Pos        delta,
                             FT_Pos        xx1,
                             FT_Pos        xx2,
                             AF_WarpScore  base_distort,
                             AF_Segment    segments,
                             FT_UInt       num_segments )
{
  FT_Int        idx_min, idx_max, idx0;
  FT_UInt       nn;
  AF_WarpScore  scores[65];


  for ( nn = 0; nn < 65; nn++ )
    scores[nn] = 0;

  idx0 = xx1 - warper->t1;

  /* compute minimum and maximum indices */
  {
    FT_Pos  xx1min = warper->x1min;
    FT_Pos  xx1max = warper->x1max;
    FT_Pos  w      = xx2 - xx1;


    if ( xx1min + w < warper->x2min )
      xx1min = warper->x2min - w;

    xx1max = warper->x1max;
    if ( xx1max + w > warper->x2max )
      xx1max = warper->x2max - w;

    idx_min = xx1min - warper->t1;
    idx_max = xx1max - warper->t1;

    if ( idx_min < 0 || idx_min > idx_max || idx_max > 64 )
    {
      FT_TRACE5(( "invalid indices:\n"
                  "  min=%d max=%d, xx1=%ld xx2=%ld,\n"
                  "  x1min=%ld x1max=%ld, x2min=%ld x2max=%ld\n",
                  idx_min, idx_max, xx1, xx2,
                  warper->x1min, warper->x1max,
                  warper->x2min, warper->x2max ));
      return;
    }
  }

  for ( nn = 0; nn < num_segments; nn++ )
  {
    FT_Pos  len = segments[nn].max_coord - segments[nn].min_coord;
    FT_Pos  y0  = FT_MulFix( segments[nn].pos, scale ) + delta;
    FT_Pos  y   = y0 + ( idx_min - idx0 );
    FT_Int  idx;


    /* score the length of the segments for the given range */
    for ( idx = idx_min; idx <= idx_max; idx++, y++ )
      scores[idx] += af_warper_weights[y & 63] * len;
  }

  /* find best score */
  {
    FT_Int  idx;


    for ( idx = idx_min; idx <= idx_max; idx++ )
    {
      AF_WarpScore  score = scores[idx];
      AF_WarpScore  distort = base_distort + ( idx - idx0 );


      if ( score > warper->best_score         ||
           ( score == warper->best_score    &&
             distort < warper->best_distort ) )
      {
        warper->best_score   = score;
        warper->best_distort = distort;
        warper->best_scale   = scale;
        warper->best_delta   = delta + ( idx - idx0 );
      }
    }
  }
}


/* Compute optimal scaling and delta values for a given glyph and */
/* dimension.                                                     */

FT_LOCAL_DEF( void )
af_warper_compute( AF_Warper      warper,
                   AF_GlyphHints  hints,
                   AF_Dimension   dim,
                   FT_Fixed      *a_scale,
                   FT_Pos        *a_delta )
{
  AF_AxisHints  axis;
  AF_Point      points;

  FT_Fixed      org_scale;
  FT_Pos        org_delta;

  FT_UInt       nn, num_points, num_segments;
  FT_Int        X1, X2;
  FT_Int        w;

  AF_WarpScore  base_distort;
  AF_Segment    segments;


  /* get original scaling transformation */
  if ( dim == AF_DIMENSION_VERT )
  {
    org_scale = hints->y_scale;
    org_delta = hints->y_delta;
  }
  else
  {
    org_scale = hints->x_scale;
    org_delta = hints->x_delta;
  }

  warper->best_scale   = org_scale;
  warper->best_delta   = org_delta;
  warper->best_score   = INT_MIN;
  warper->best_distort = 0;

  axis         = &hints->axis[dim];
  segments     = axis->segments;
  num_segments = axis->num_segments;
  points       = hints->points;
  num_points   = hints->num_points;

  *a_scale = org_scale;
  *a_delta = org_delta;

  /* get X1 and X2, minimum and maximum in original coordinates */
  if ( num_segments < 1 )
    return;

#if 1
  X1 = X2 = points[0].fx;
  for ( nn = 1; nn < num_points; nn++ )
  {
    FT_Int  X = points[nn].fx;


    if ( X < X1 )
      X1 = X;
    if ( X > X2 )
      X2 = X;
  }
#else
  X1 = X2 = segments[0].pos;
  for ( nn = 1; nn < num_segments; nn++ )
  {
    FT_Int  X = segments[nn].pos;


    if ( X < X1 )
      X1 = X;
    if ( X > X2 )
      X2 = X;
  }
#endif

  if ( X1 >= X2 )
    return;

  warper->x1 = FT_MulFix( X1, org_scale ) + org_delta;
  warper->x2 = FT_MulFix( X2, org_scale ) + org_delta;

  warper->t1 = AF_WARPER_FLOOR( warper->x1 );
  warper->t2 = AF_WARPER_CEIL( warper->x2 );

  /* examine a half pixel wide range around the maximum coordinates */
  warper->x1min = warper->x1 & ~31;
  warper->x1max = warper->x1min + 32;
  warper->x2min = warper->x2 & ~31;
  warper->x2max = warper->x2min + 32;

  if ( warper->x1max > warper->x2 )
    warper->x1max = warper->x2;

  if ( warper->x2min < warper->x1 )
    warper->x2min = warper->x1;

  warper->w0 = warper->x2 - warper->x1;

  if ( warper->w0 <= 64 )
  {
    warper->x1max = warper->x1;
    warper->x2min = warper->x2;
  }

  /* examine (at most) a pixel wide range around the natural width */
  warper->wmin = warper->x2min - warper->x1max;
  warper->wmax = warper->x2max - warper->x1min;

#if 1
  /* some heuristics to reduce the number of widths to be examined */
  {
    int  margin = 16;


    if ( warper->w0 <= 128 )
    {
       margin = 8;
       if ( warper->w0 <= 96 )
         margin = 4;
    }

    if ( warper->wmin < warper->w0 - margin )
      warper->wmin = warper->w0 - margin;

    if ( warper->wmax > warper->w0 + margin )
      warper->wmax = warper->w0 + margin;
  }

  if ( warper->wmin < warper->w0 * 3 / 4 )
    warper->wmin = warper->w0 * 3 / 4;

  if ( warper->wmax > warper->w0 * 5 / 4 )
    warper->wmax = warper->w0 * 5 / 4;
#else
  /* no scaling, just translation */
  warper->wmin = warper->wmax = warper->w0;
#endif

  for ( w = warper->wmin; w <= warper->wmax; w++ )
  {
    FT_Fixed  new_scale;
    FT_Pos    new_delta;
    FT_Pos    xx1, xx2;


    /* compute min and max positions for given width,       */
    /* assuring that they stay within the coordinate ranges */
    xx1 = warper->x1;
    xx2 = warper->x2;
    if ( w >= warper->w0 )
    {
      xx1 -= w - warper->w0;
      if ( xx1 < warper->x1min )
      {
        xx2 += warper->x1min - xx1;
        xx1  = warper->x1min;
      }
    }
    else
    {
      xx1 -= w - warper->w0;
      if ( xx1 > warper->x1max )
      {
        xx2 -= xx1 - warper->x1max;
        xx1  = warper->x1max;
      }
    }

    if ( xx1 < warper->x1 )
      base_distort = warper->x1 - xx1;
    else
      base_distort = xx1 - warper->x1;

    if ( xx2 < warper->x2 )
      base_distort += warper->x2 - xx2;
    else
      base_distort += xx2 - warper->x2;

    /* give base distortion a greater weight while scoring */
    base_distort *= 10;

    new_scale = org_scale + FT_DivFix( w - warper->w0, X2 - X1 );
    new_delta = xx1 - FT_MulFix( X1, new_scale );

    af_warper_compute_line_best( warper, new_scale, new_delta, xx1, xx2,
                                 base_distort,
                                 segments, num_segments );
  }

  {
    FT_Fixed  best_scale = warper->best_scale;
    FT_Pos    best_delta = warper->best_delta;


    hints->xmin_delta = FT_MulFix( X1, best_scale - org_scale )
                        + best_delta;
    hints->xmax_delta = FT_MulFix( X2, best_scale - org_scale )
                        + best_delta;

    *a_scale = best_scale;
    *a_delta = best_delta;
  }
}

#else /* !AF_CONFIG_OPTION_USE_WARPER */

/* ANSI C doesn't like empty source files */
typedef int _af_warp_dummy;

#endif /* !AF_CONFIG_OPTION_USE_WARPER */

/* END */
